Cathode sleeve



June 3, 1941. K. G. BUCKLIN 2,244,356

'CATHODE SLEEVE Filed March 28, 1940 [NV EN TOR.

E/V/VETH G. EUCKL/N BY I %% law ATTORNEY.

Patented June 3, 1941 o 'rnoDE SLEEVE Kenneth G. Bucklin, West Orange,N. J assignor to Radio Corporation of America, a Delaware corporationApplication March 28, 1940, Serial No. 326,347 Claims. (Cl. 250-275) Myinvention relates to electron dischargede- Vices particularly to cathodesleeves ofth indirectly heated type for such devices.

Insulating spacers for electrode assemblies in radio tubes are usuallyslipped over opposite ends of the cathode sleeve and onto the ends ofthe grid and plate side rods to hold the electrodes in insulated spacedrelation. In some electrode assemblies, however, it is desirable andeven necessary first to assemble the grids and plates with the spacersand then to pass the cathode sleeve through its hole in one spacer andinto a registering hole in the other spacer. As the oxide coated portionof the sleeve passes through the hole, it is scraped and damaged.

The object of my invention is an improved cathode sleeve that can beeasily mounted in an electrode assembly without damage to the surface ofthe cathode.

The characteristic features of my invention are defined in the appendedclaims and one embodiment is described in the following specificationand shown in the accompanying drawing in which Figure 1 is anelevational view of an electrode assembly embodying my novel cathode,Figure 2 is a detailed View of a cathode sleeve constructed according tomy invention, and Figure 3 is a sectional View of my cathode taken online 3-3 of Figure 2.

The particular electron discharge device shown in the drawing forillustrating my invention comprises a metal envelope I closed at itslower end with a non-reentrant or button type stem 2, into which issealed the lead conductors for the electrodes. The electrode assemblywithin the envelope comprises a tubular cathode sleeve or cylinder 3with two spaced emitting sections 4 and 5, around the lower emittingsection being mounted an anode 6 and a grid 1. The anode and grid aresupported at their ends by spaced parallel insulating spacers 8 and 9,preferably of mica, and the cathode sleeve is held in registering holesin the two spacers with the upper spacer 8 engaging the sleeveintermediate the two emitting sections and the lower spacer engaging thelower end of the sleeve. The two emitting sections of the sleeve areactivated, preferably by coatings of the usual active metal oxides, suchas barium strontium oxide, and the lower emitting section of the cathodein combination with the grid and the anode functions in the usual way asa triode.

In the particular tube shown, two diode plates l0 comprising a fiatsheet of metal pressed out of thin metal stock, such as nickel, aremounted on ml sit i es th upper t n see-tie? ach' en ef sub ta ti l fh fd 91%.? with two'fiat leg portions ll integral with the lower edge'ofeach plate and extending "clown wardly and aflixed to thetwo spa'cers'toholdthe diode anodes and cathode in rigid fixed spaced relation.

in manufacture the ends of the anode 6 and grid are esseqm o theiropenings in'thespacrs and the two flat anodes are added by slippingtheir arms downwardly over the edges of the spacers and their ends areclinched to lock the electrode assembly together. The electrode assemblyis supported on the stem with two support rods 12 passing through thespacers and joined at their lower ends to upstanding ears on the stem.

The cathode sleeve in this electrode assembly must be passed through thehole in one of the spacers and the inserted end of the sleeve threadedinto the registering hole in the other spacer. According to my inventionthe hole I3 in the upper spacer is made larger in diameter than thesleeve and the sleeve is lowered into the assembly from the upper end.As shown in greater detail in Figures 2 and 3 the sleeve is centered inthe hole by beads l4, preferably integral with the sleeve, of uniformheight and evenly spaced around the sleeve. These beads may be elongatedand slightly tapered longitudinally of the sleeve to wedge the sleeve inplace, as the edge of the hole rides up onto the beads. To prevent thesleeve from slipping through the hole, at least one of the beads isembossed near its end with a raised shoulder E5. The two-step embossingmay be easily pressed in the Walls of the sleeve by die punches, ithaving been found convenient in manufacture to emboss the flat sheetmetal blanks from which the sleeves are made before they are rolled intocylinders and seamed along one side by welding or by the conventionallock seam. In embossing and drawing out the metal as shown, the sides ofthe blank are sometimes pulled in. When my cathode must be made of verythin sheet metal it is preferred first to draw the beads M and shoulderl5, then trim the sides of the blank to the proper size, and then rollinto cylinders and form the seam, Seamless cathode tubing may beembossed from the inside with suitable mandrels. For most purposes threebeads for centering the sleeve in its hole are sufficient and only onebead need be embossed at its end for providing a positive stop for thesleeve. Each of the beads may of course be embossed at its end with theraised shoulder. A cathode sleeve with an outside diameter of .045 inchand a wall thickness of .002 inch when provided with three beads .005inch high, one of which is embossed at its end to a height of .009 inch,is easily slid into its slightly oversize spacer hole about .05 inch indiameter without scratching the active metal coatings. The beadsautomatically center the sleeve in the hole as the shoulder I5 comes torest on the spacer. A cathode tab fixed to the lower end of the sleeveand to a lead-in wire may hold the sleeve against removal.

My improved cathode sleeve is easy to manufacture and is easy to mountin an electrode assembly without damage to the surface of the cathode.My improved sleeve is firmly held in centered position in the assemblyand is fixed against longitudinal movement.

I claim:

1. A cathode for an electron discharge device comprising a metal tubularcylinder, an integral embossing in the wall of said cylinder, saidembossing having two steps, one step being farther above the surface ofthe cylinder than the other step.

2. An electron discharge device comprising a flat insulating spacer withan opening, a cathode sleeve extending through said opening, a bead forspacing said sleeve from the side of said opening and a boss on saidbead overlying the edge of said opening.

3. In an electron discharge device, an insulating spacer with anopening, a sleeve extending through said opening, a bead on the side ofsaid sleeve in said opening for spacing said sleeve from the side ofsaid opening, and means for preventing longitudinal movement of saidsleeve in one direction through said opening comprising a boss on saidsleeve of greater height than said bead, said boss overlying the edge ofsaid open mg.

4. In combination a tubular cathode, a pair of spacers, said cathodebeing supported in registering openings in said spacers, the opening inone spacer being larger than the outside diameter of said sleeve, araised head on the side of said sleeve in said one of said openings, anda boss on said sleeve overlying the edge of said opening.

5. A cathode for an electron discharge device comprising a metal tubularcylinder, at least three elongated and relatively narrow beads extendinglongitudinally of said cylinder spaced circumferentially around the wallof the cylinder, one of said beads having adjacent its end and integraltherewith a raised portion of greater height than said head.

KENNETH G. BUCKLIN.

